1. Field of the Invention
The present invention relates to an axial flow fluid compressor and, in particular, a compressor for compressing, for example, a refrigerant in a refrigerating cycle.
2. Description of the Related Art
Conventionally, various types of compressors are known, such as a reciprocating type and rotary type. In these compressors, a driving section includes a crank shaft, etc., for transmitting a rotational force and a compression section for receiving the rotational force from the driving section to perform a compressing operation. However, many associated parts are involved in the compressor, resulting in a complex compressor.
Further, a check valve is required on the discharge side to enhance a compression efficiency, but because of a very great pressure difference created across both sides of the check valve a gas is liable to leak out of the valve and the compression efficiency is lowered. In order to overcome such a problem, high accuracy is required for the associated parts and upon assembly. A greater cost is also involved in the manufacture of the compressor.
Recently, proposals have been made to provide an axial flow fluid compressor (U.S. Pat. Nos. 4,871,304; 4,872,802; 4,875,842, etc.). The fluid compressor can achieve sealing with a relatively simple arrangement, an effective compression and a ready manufacture and assembly of associated parts.
This type of fluid compressor (hereinafter referred to as a compressor) 101 is as shown in FIG. 5.
In the compressor 101, an electrically operating element 102 and compression element 103 are held in place in a closed casing. The electrically operating element 102 includes an annular stator 105 and annular rotor 106 provided inside the stator 105. The compression element 103 includes a cylinder 107 with the rotor 106 coaxially mounted on the outer periphery of the cylinder 107. The cylinder 107 is rotatably supported by a main bearing 108 at one end and the main bearing 108 is fixed to the closed casing 104 by a frame 109 jointed by a means, such as welding, to the inner surface of the closed casing 104.
A rotating rod 110 of cylindrical shape is held in the cylinder 107 in an axial direction. The center axis A of the rotating rod 110 is located eccentric with the center axis B of the cylinder 107. The rod 110 is rotatably supported by the bearings 108 and 111 at both ends. In FIG. 5, e represents an amount of eccentricity.
A spiral groove 112 is provided on the outer periphery of the rotating rod 110 with its pitch gradually varied. A spiral blade 113 is fitted in the groove 112. Respective portions of the blade 113 are displaceable relative to the groove 112 and the outer periphery of the blade 113 is slidable on the inner wall of the cylinder 107 in intimate contact state.
A plurality of working chambers 114 are formed between the inner wall of the cylinder 107 and the outer periphery of the rotating rod 110. The respective working chamber 114 is defined as a substantially crescent spacing extending from an area of contact of the rotating rod 110 with the inner wall of the cylinder 107 to the next area of contact. The working chambers 114, . . . are gradually decreased in their capacity from a suction side to a discharge side of the cylinder 107.
Upon the turning ON of the electrically operating element 102, the rotor 106 is rotated, causing the compression element to be rotationally driven. The cylinder 107, together with the rotor 106, is rotated as one unit and the rotational force of the cylinder 107 is transmitted through a rotational force transmission mechanism 115 to the rotating rod 110. The cylinder 107 and rod 110 are, while being displaced relative to each other, rotated in a synchronous way.
A working fluid, such as a gaseous refrigerant, is sucked into the cylinder 107 and carried past the respective working chambers 114, . . . sequentially. The working fluid is gradually compressed in a route from the suction side to the discharged side of the cylinder 107.
In this type of compressor, a narrow, uniform spacing, that is a motor air gap 116, is formed between the stator 105 and the rotor 106. Since the cylinder 107 is journaled in the main bearing 108 at the one end and the main bearing 108 is supported on the frame 108, it is necessary to provide exact perpendicularity to a seat surface 117 of the frame 109.
However, as the frame 109 is fixed to the closed casing 104 by the means, such as welding, no adequate perpendicularity is imparted to the seat surface 117 of the frame 109 if the frame 109 is simply mounted on the closed casing 104. It is, therefore, necessary to finish-shape the seat surface 117 of the frame 109 by machinery after it has been mounted in place in the compressor, and to enhance the aforementioned perpendicularity. This finish-shaping operation has to be done in the closed casing 2 and hence is complex and time-consuming.